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SubjectRe: [PATCH 30/30] KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE
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On 5/29/20 8:39 AM, Paolo Bonzini wrote:
> Similar to VMX, the state that is captured through the currently available
> IOCTLs is a mix of L1 and L2 state, dependent on whether the L2 guest was
> running at the moment when the process was interrupted to save its state.
>
> In particular, the SVM-specific state for nested virtualization includes
> the L1 saved state (including the interrupt flag), the cached L2 controls,
> and the GIF.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/include/uapi/asm/kvm.h | 17 +++-
> arch/x86/kvm/cpuid.h | 5 ++
> arch/x86/kvm/svm/nested.c | 147 ++++++++++++++++++++++++++++++++
> arch/x86/kvm/svm/svm.c | 1 +
> arch/x86/kvm/vmx/nested.c | 5 --
> arch/x86/kvm/x86.c | 3 +-
> 6 files changed, 171 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 3f3f780c8c65..12075a9de1c1 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -385,18 +385,22 @@ struct kvm_sync_regs {
> #define KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT (1 << 4)
>
> #define KVM_STATE_NESTED_FORMAT_VMX 0
> -#define KVM_STATE_NESTED_FORMAT_SVM 1 /* unused */
> +#define KVM_STATE_NESTED_FORMAT_SVM 1
>
> #define KVM_STATE_NESTED_GUEST_MODE 0x00000001
> #define KVM_STATE_NESTED_RUN_PENDING 0x00000002
> #define KVM_STATE_NESTED_EVMCS 0x00000004
> #define KVM_STATE_NESTED_MTF_PENDING 0x00000008
> +#define KVM_STATE_NESTED_GIF_SET 0x00000100
>
> #define KVM_STATE_NESTED_SMM_GUEST_MODE 0x00000001
> #define KVM_STATE_NESTED_SMM_VMXON 0x00000002
>
> #define KVM_STATE_NESTED_VMX_VMCS_SIZE 0x1000
>
> +#define KVM_STATE_NESTED_SVM_VMCB_SIZE 0x1000
> +
> +
> struct kvm_vmx_nested_state_data {
> __u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
> __u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
> @@ -411,6 +415,15 @@ struct kvm_vmx_nested_state_hdr {
> } smm;
> };
>
> +struct kvm_svm_nested_state_data {
> + /* Save area only used if KVM_STATE_NESTED_RUN_PENDING. */
> + __u8 vmcb12[KVM_STATE_NESTED_SVM_VMCB_SIZE];
> +};
> +
> +struct kvm_svm_nested_state_hdr {
> + __u64 vmcb_pa;
> +};
> +
> /* for KVM_CAP_NESTED_STATE */
> struct kvm_nested_state {
> __u16 flags;
> @@ -419,6 +432,7 @@ struct kvm_nested_state {
>
> union {
> struct kvm_vmx_nested_state_hdr vmx;
> + struct kvm_svm_nested_state_hdr svm;
>
> /* Pad the header to 128 bytes. */
> __u8 pad[120];
> @@ -431,6 +445,7 @@ struct kvm_nested_state {
> */
> union {
> struct kvm_vmx_nested_state_data vmx[0];
> + struct kvm_svm_nested_state_data svm[0];
> } data;
> };
>
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index 63a70f6a3df3..05434cd9342f 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -303,4 +303,9 @@ static __always_inline void kvm_cpu_cap_check_and_set(unsigned int x86_feature)
> kvm_cpu_cap_set(x86_feature);
> }
>
> +static inline bool page_address_valid(struct kvm_vcpu *vcpu, gpa_t gpa)
> +{
> + return PAGE_ALIGNED(gpa) && !(gpa >> cpuid_maxphyaddr(vcpu));
> +}
> +
> #endif
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index c712fe577029..6b1049148c1b 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -25,6 +25,7 @@
> #include "trace.h"
> #include "mmu.h"
> #include "x86.h"
> +#include "cpuid.h"
> #include "lapic.h"
> #include "svm.h"
>
> @@ -238,6 +239,8 @@ static void load_nested_vmcb_control(struct vcpu_svm *svm,
> {
> copy_vmcb_control_area(&svm->nested.ctl, control);
>
> + /* Copy it here because nested_svm_check_controls will check it. */
> + svm->nested.ctl.asid = control->asid;
> svm->nested.ctl.msrpm_base_pa &= ~0x0fffULL;
> svm->nested.ctl.iopm_base_pa &= ~0x0fffULL;
> }
> @@ -930,6 +933,150 @@ int nested_svm_exit_special(struct vcpu_svm *svm)
> return NESTED_EXIT_CONTINUE;
> }
>
> +static int svm_get_nested_state(struct kvm_vcpu *vcpu,
> + struct kvm_nested_state __user *user_kvm_nested_state,
> + u32 user_data_size)
> +{
> + struct vcpu_svm *svm;
> + struct kvm_nested_state kvm_state = {
> + .flags = 0,
> + .format = KVM_STATE_NESTED_FORMAT_SVM,
> + .size = sizeof(kvm_state),
> + };
> + struct vmcb __user *user_vmcb = (struct vmcb __user *)
> + &user_kvm_nested_state->data.svm[0];
> +
> + if (!vcpu)
> + return kvm_state.size + KVM_STATE_NESTED_SVM_VMCB_SIZE;
> +
> + svm = to_svm(vcpu);
> +
> + if (user_data_size < kvm_state.size)
> + goto out;
> +
> + /* First fill in the header and copy it out. */
> + if (is_guest_mode(vcpu)) {
> + kvm_state.hdr.svm.vmcb_pa = svm->nested.vmcb;
> + kvm_state.size += KVM_STATE_NESTED_SVM_VMCB_SIZE;
> + kvm_state.flags |= KVM_STATE_NESTED_GUEST_MODE;
> +
> + if (svm->nested.nested_run_pending)
> + kvm_state.flags |= KVM_STATE_NESTED_RUN_PENDING;
> + }
> +
> + if (gif_set(svm))
> + kvm_state.flags |= KVM_STATE_NESTED_GIF_SET;
> +
> + if (copy_to_user(user_kvm_nested_state, &kvm_state, sizeof(kvm_state)))
> + return -EFAULT;
> +
> + if (!is_guest_mode(vcpu))
> + goto out;
> +
> + /*
> + * Copy over the full size of the VMCB rather than just the size
> + * of the structs.
> + */
> + if (clear_user(user_vmcb, KVM_STATE_NESTED_SVM_VMCB_SIZE))
> + return -EFAULT;
> + if (copy_to_user(&user_vmcb->control, &svm->nested.ctl,
> + sizeof(user_vmcb->control)))
> + return -EFAULT;
> + if (copy_to_user(&user_vmcb->save, &svm->nested.hsave->save,
> + sizeof(user_vmcb->save)))
> + return -EFAULT;
> +
> +out:
> + return kvm_state.size;
> +}
> +
> +static int svm_set_nested_state(struct kvm_vcpu *vcpu,
> + struct kvm_nested_state __user *user_kvm_nested_state,
> + struct kvm_nested_state *kvm_state)
> +{
> + struct vcpu_svm *svm = to_svm(vcpu);
> + struct vmcb *hsave = svm->nested.hsave;
> + struct vmcb __user *user_vmcb = (struct vmcb __user *)
> + &user_kvm_nested_state->data.svm[0];
> + struct vmcb_control_area ctl;
> + struct vmcb_save_area save;
> + u32 cr0;
> +
> + if (kvm_state->format != KVM_STATE_NESTED_FORMAT_SVM)
> + return -EINVAL;
> +
> + if (kvm_state->flags & ~(KVM_STATE_NESTED_GUEST_MODE |
> + KVM_STATE_NESTED_RUN_PENDING |
> + KVM_STATE_NESTED_GIF_SET))
> + return -EINVAL;
> +
> + /*
> + * If in guest mode, vcpu->arch.efer actually refers to the L2 guest's
> + * EFER.SVME, but EFER.SVME still has to be 1 for VMRUN to succeed.
> + */
> + if (!(vcpu->arch.efer & EFER_SVME)) {
> + /* GIF=1 and no guest mode are required if SVME=0. */
> + if (kvm_state->flags != KVM_STATE_NESTED_GIF_SET)
> + return -EINVAL;
> + }
> +
> + /* SMM temporarily disables SVM, so we cannot be in guest mode. */
> + if (is_smm(vcpu) && (kvm_state->flags & KVM_STATE_NESTED_GUEST_MODE))
> + return -EINVAL;
> +
> + if (!(kvm_state->flags & KVM_STATE_NESTED_GUEST_MODE)) {


Should this be done up at the beginning of the function ? If this flag
isn't set, we probably don't want to come this far.

> + svm_leave_nested(svm);
> + goto out_set_gif;
> + }
> +
> + if (!page_address_valid(vcpu, kvm_state->hdr.svm.vmcb_pa))
> + return -EINVAL;
> + if (kvm_state->size < sizeof(*kvm_state) + KVM_STATE_NESTED_SVM_VMCB_SIZE)
> + return -EINVAL;
> + if (copy_from_user(&ctl, &user_vmcb->control, sizeof(ctl)))
> + return -EFAULT;
> + if (copy_from_user(&save, &user_vmcb->save, sizeof(save)))
> + return -EFAULT;
> +
> + if (!nested_vmcb_check_controls(&ctl))
> + return -EINVAL;
> +
> + /*
> + * Processor state contains L2 state. Check that it is
> + * valid for guest mode (see nested_vmcb_checks).
> + */
> + cr0 = kvm_read_cr0(vcpu);
> + if (((cr0 & X86_CR0_CD) == 0) && (cr0 & X86_CR0_NW))
> + return -EINVAL;


Does it make sense to create a wrapper for the CR0 checks ? We have
these checks in nested_vmcb_check_controls() also.

> +
> + /*
> + * Validate host state saved from before VMRUN (see
> + * nested_svm_check_permissions).
> + * TODO: validate reserved bits for all saved state.
> + */
> + if (!(save.cr0 & X86_CR0_PG))
> + return -EINVAL;
> +
> + /*
> + * All checks done, we can enter guest mode. L1 control fields
> + * come from the nested save state. Guest state is already
> + * in the registers, the save area of the nested state instead
> + * contains saved L1 state.
> + */
> + copy_vmcb_control_area(&hsave->control, &svm->vmcb->control);
> + hsave->save = save;
> +
> + svm->nested.vmcb = kvm_state->hdr.svm.vmcb_pa;
> + load_nested_vmcb_control(svm, &ctl);
> + nested_prepare_vmcb_control(svm);
> +
> +out_set_gif:
> + svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));
> + return 0;
> +}
> +
> struct kvm_x86_nested_ops svm_nested_ops = {
> .check_events = svm_check_nested_events,
> + .get_state = svm_get_nested_state,
> + .set_state = svm_set_nested_state,
> };
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index b4db9a980469..3871bfb40594 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -1193,6 +1193,7 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
> svm->avic_is_running = true;
>
> svm->nested.hsave = page_address(hsave_page);
> + clear_page(svm->nested.hsave);
>
> svm->msrpm = page_address(msrpm_pages);
> svm_vcpu_init_msrpm(svm->msrpm);
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 51ebb60e1533..106fc6fceb97 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -437,11 +437,6 @@ static void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu,
> }
> }
>
> -static bool page_address_valid(struct kvm_vcpu *vcpu, gpa_t gpa)
> -{
> - return PAGE_ALIGNED(gpa) && !(gpa >> cpuid_maxphyaddr(vcpu));
> -}
> -
> static int nested_vmx_check_io_bitmap_controls(struct kvm_vcpu *vcpu,
> struct vmcs12 *vmcs12)
> {
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f0fa610bed91..d4aa7dc662d5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4628,7 +4628,8 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>
> if (kvm_state.flags &
> ~(KVM_STATE_NESTED_RUN_PENDING | KVM_STATE_NESTED_GUEST_MODE
> - | KVM_STATE_NESTED_EVMCS | KVM_STATE_NESTED_MTF_PENDING))
> + | KVM_STATE_NESTED_EVMCS | KVM_STATE_NESTED_MTF_PENDING
> + | KVM_STATE_NESTED_GIF_SET))
> break;
>
> /* nested_run_pending implies guest_mode. */

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